m0n0wall Forum - sharing printers between two networks

being new to mono, I would appreciate some hints on how to best resolve the following issue:

Network A is a "closed" production network with 6 PCs and 3 network printers. All the devices are on 192.168.0.x and connected through a (managed)switch.

Network B 192.168.178.x is connected via a wireless router to the internet and is used by 4 PCs either through the wireless connection or through the router's 4 ethernet ports.

The two networks are not physicaly connected.All devices use fixed IP addresses. At present the printers are in network A.

I would like to put betwen A and B, a monowall(VM) to do the following:

Allow all PCs from network B to print to all the network printers (in network A) but keep A as isolated as possible.
Block all outgoing trafficfrom network A, but allow FTP, NTP and SMTP from network A to be routed through network B to the WAN

Looks like NAT could be configured to do it, but I must admit I do not realy understand the m0n0wall NAT settings yet. I would be gratefull if somebody could give me an example of the settings, to achieve what I described above or maybe just point to a usefull source.
Thanks